Systems biology expands on general systems theory as the "omics'' era rapidly progresses. Although systems biology has been institutionalized as an interdisciplinary framework in the biosciences, it is not yet apparent in nursing. This article introduces systems biology for nursing science by presenting an overview of the theory. This framework for the study of organisms from molecular to environmental levels includes iterations of computational modeling, experimentation, and theory building. Synthesis of complex biological processes as whole systems rather than isolated parts is emphasized. Pros and cons of systems biology are discussed, and relevance of systems biology to nursing is described. Nursing research involving molecular, physiological, or biobehavioral questions may be guided by and contribute to the developing science of systems biology. Nurse scientists can proactively incorporate systems biology into their investigations as a framework for advancing the interdisciplinary science of human health care. Systems biology has the potential to advance the research and practice goals of the National Institute for Nursing Research in the National Institutes of Health Roadmap initiative.